With a low level of transparency about donors, some advocacy groups open themselves up to accusations.

What is astroturfing? The practice for companies or organizations to secretly fund what appear to be grassroots advocacy groups with popular support has a long history in U.S. public policy debates. But it can be difficult to determine whether specific groups are true astroturfers. One person's astroturf group may be another's legitimate advocacy group, depending on perspective.

Funding transparency isn't the only measure of an advocacy group's credibility. Some advocates argue it's just one of several factors, including the history of a group's work in policy. Most of the groups we examined have worked on tech policy issues for several years, and some of the groups with the lowest grades employ advocates who have decades of experience in tech policy, including, in some cases, time working inside government.

Still, some companies have a long track record of funding "fake activism," said Holmes Wilson, co-founder of pro-net neutrality group Fight for the Future. "I have to say I've never seen it done well," he said. "To do good activism, you have to believe in what you're doing, to your core. These PR consultants don't, and it shows."

The issues of astroturfing and funding transparency are connected to the influence that think tanks and advocacy groups wield. It's difficult to measure their specific influence, because measuring effectiveness is a bit of a dark art. Advocacy groups point to a number of factors that should be considered, including legislation and regulation passed or defeated, research cited, member actions taken and media coverage.

In some cases, several groups advocate the same position, or motivate an overlapping group of constituents, making it difficult to separate each advocacy group's influence. Many of the 14 groups in IDG News Service's transparency investigation have testified before Congress on tech-related issues, have had their work cited in FCC rulemaking proceedings and have been quoted frequently in the media.

Looking beyond funding transparency Several advocacy groups encourage people interested in net neutrality and other issues to look beyond funding transparency to judge the value of a group's positions.

In a complicated technical issue like net neutrality, funding transparency can sidetrack a legitimate and needed debate, said Doug Brake, telecommunications policy analyst with the Information Technology and Innovation Foundation, a think tank opposed to reclassification of broadband. At legitimate think tanks, "ideas come first," ahead of the views of donors, he said.

A public outcry urging the FCC to pass net neutrality rules has obscured some valid issues, including legitimate needs for network management, Brake said. "We've lost a lot of nuance in the debate," Brake said. "We need to be looking at the actual solutions to these sorts of problems that are based in engineering and economic fact."